Re: [PATCH 5.15.y] mptcp: don't always assume copied data in mptcp_cleanup_rbuf()

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

The upstream commit SHA1 provided is correct: 551844f26da2a9f76c0a698baaffa631d1178645

WARNING: Author mismatch between patch and upstream commit:
Backport author: "Matthieu Baerts (NGI0)"<matttbe@kernel.org>
Commit author: Paolo Abeni<pabeni@redhat.com>


Status in newer kernel trees:
6.12.y | Present (different SHA1: 10a641cad465)
6.6.y | Present (different SHA1: f61e663d78ff)
6.1.y | Present (different SHA1: 91b493f15d65)
5.15.y | Not found

Note: The patch differs from the upstream commit:
---
1:  551844f26da2a ! 1:  3fe05f72a15ff mptcp: don't always assume copied data in mptcp_cleanup_rbuf()
    @@ Metadata
      ## Commit message ##
         mptcp: don't always assume copied data in mptcp_cleanup_rbuf()
     
    +    commit 551844f26da2a9f76c0a698baaffa631d1178645 upstream.
    +
         Under some corner cases the MPTCP protocol can end-up invoking
         mptcp_cleanup_rbuf() when no data has been copied, but such helper
         assumes the opposite condition.
    @@ Commit message
         Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
         Link: https://patch.msgid.link/20241230-net-mptcp-rbuf-fixes-v1-2-8608af434ceb@kernel.org
         Signed-off-by: Jakub Kicinski <kuba@kernel.org>
    +    [ Conflicts in this version, because commit 581302298524 ("mptcp: error
    +      out earlier on disconnect") has not been backported to this version,
    +      and there was no need to do so. The only conflict was in protocol.c,
    +      and easy to resolve: the context was different, but the same addition
    +      can still be made at the same spot in mptcp_recvmsg(). ]
    +    Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
     
      ## net/mptcp/protocol.c ##
     @@ net/mptcp/protocol.c: static void mptcp_send_ack(struct mptcp_sock *msk)
    @@ net/mptcp/protocol.c: static int mptcp_recvmsg(struct sock *sk, struct msghdr *m
      
      		pr_debug("block timeout %ld\n", timeo);
     +		mptcp_cleanup_rbuf(msk, copied);
    - 		err = sk_wait_data(sk, &timeo, NULL);
    - 		if (err < 0) {
    - 			err = copied ? : err;
    -@@ net/mptcp/protocol.c: static int mptcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len,
    - 		}
    + 		sk_wait_data(sk, &timeo, NULL);
      	}
      
     +	mptcp_cleanup_rbuf(msk, copied);
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-5.15.y       |  Success    |  Success   |